Mucuna argentea T.M.Moura, G.P.Lewis & A.M.G.Azevedo

Distribution

Biogeografic region: Amazonia, Andean, Guiana Shield. Elevation range: 160–1300 m a.s.l. Native to Colombia. Colombian departments: Amazonas, Caquetá, Cauca, Meta, Putumayo, Vaupés.

Habit

Climbing.

Conservation

National Red List of Colombia (2021): EN.

Moura, T.M., Lewis, G.P., Mansano, V.F. et al. 2013. Three new species of Mucuna (Leguminosae: Papilionoideae: Phaseoleae) from South America. Kew Bulletin 68: 143. DOI https://doi.org/10.1007/s12225-012-9429-6

Type

Type: Colombia, Caquetá Peña Roja, Kats & Dulmen AVD265 (holotype K!; isotypes COAH!, MO!).

Morphology General Habit

Lianas; stems sericeous

Morphology Leaves

Leaves alternate, 3-foliolate; stipules c. 5 × 1 mm, triangular, sericeous; pulvinus cylindrical, 10 × 3 mm, with a dense indumentum of erect or appressed hairs; petiole 10 – 12 cm long, angular, sericeous; rachis 1 – 3 cm long, angular, sericeous; stipels linear, 3 mm long, sericeous; petiolules 5 – 10 mm long, sericeous, the hairs more dense than on the petiole and rachis; leaflet blades ovate to elliptic, occasionally obovate, apical leaflet 12 – 17 × 9 – 12 cm, lateral leaflets 12 – 15 × 7 – 10 cm, asymmetrical, all blades obtuse or rounded at base, acuminate or cuspidate at apex, sparsely sericeous adaxially, densely silvery sericeous abaxially, venation eucamptodromous, secondary veins in 7 – 8 pairs per leaflet

Morphology Reproductive morphology Inflorescences

Inflorescence axillary, pseudo-umbelliform, pendent; peduncle 7 – 10 cm long, sericeous; primary axis condensed, all flowers inserted close together at the apex; primary bracts (at base of whole inflorescence axis) caducous (3 cm long, which fall before anthesis); secondary bracts (at base of each node or individual flower) absent; pedicels 1.5 – 2 cm long sericeous; flowers 8 – 9 cm long

Morphology Reproductive morphology Flowers Calyx

Calyx campanulate, 2 – 2.5 cm long, with long appressed hairs on both surfaces; lobes 4, the adaxial lobe formed by two connate sepals, 5 × 3 mm, apex obtuse, the other three lobes 5 – 7 × 3 mm long, apex acute

Morphology Reproductive morphology Flowers Corolla

Corolla reported to be yellow [Dulmen 265 (K); Klug 2265 (K); Cardenas et al-6116 (K)]; standard 5 – 6 × 3 cm, broadly elliptic, base attenuate, apex retuse, the claw c. 1 – 2 mm long, glabrous; wing petals 7 – 9 × 1 – 1.5 cm, oblong-obovate, base attenuate, apex obtuse, pubescent at base, the claw c. 7 – 10 mm; keel petals 7 – 8.5 × 0.7 – 0.8 cm, oblong, base attenuate, apex acute, pubescent at base, the claw c. 1 mm long

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens 10, diadelphous, with nine fused for about 75% of their filament length, one free; filaments 8 cm long, glabrous; anthers oblong, basifixed, 4 mm long, the connective tomentose

Morphology Reproductive morphology Flowers Gynoecium

Gynoecium 9 – 10 cm long; ovary sessile, oblong, 10 × 2 mm, densely sericeous, 3 – 4-ovulate; style 8 – 9 cm long, densely sericeous, glabrescent at apex, stigma villous

Morphology Reproductive morphology Fruits

Young fruits 17 × 3 cm, base attenuate, apex apiculate, valve surfaces with an indumentum of long urticating hairs and shorter, dense, dark-coloured hairs, but lacking lamellate ornamentation and without winged margins

Morphology Reproductive morphology Seeds

Immature seeds 2 – 4 per pod, with the hilum extending around most of the seed circumference; mature seeds not seen

Figures

Fig. 1.

Distribution

Mucunaargentea occurs in Ecuador, Peru and the Amazonian region of Colombia (Map 1).

Ecology

Field labels report the species from ‘selva’ and secondary forest, frequently close to rivers. In general it occurs at low elevations, alt. 160 – 450 m; it also has been reported at 1300 m in Meta, Colombia.

Conservation

Mucunaargentea occurs predominantly in Amazonian forest, especially close to rivers, where it prefers undisturbed habitats. Based on herbarium specimens it appears that M. argentea is relatively common in Colombia but rare in Ecuador and Peru and, according to IUCN criteria (2001), this species can be temporarily assessed as Endangered (EN).

Phenology

Flowering June – Jan., with most flowering specimens in herbaria reported to have been collected in Aug.; fruiting Aug. – Nov.

Note

The specific epithet refers to the silvery indumentum on the abaxial surface of the leaflets. Among the South American species with a pseudo-umbelliform inflorescence, Mucunaargentea is the only one that has a silvery indumentum on the abaxial surface of the leaflets. The presence of large sericeous bracts, which fall before the flowers open, is also distinctive. Specimens in herbaria are often encountered under the name M. elliptica, but in that species the hairs on the abaxial surface of the leaflets are golden-coloured and erect and the bracts are generally persistent. Only two American species have silver-coloured hairs on the abaxial surface of their leaflets as a strong taxonomic characteristic: M. argentea and M. argyrophyllaStandl. (Standley1922: 504); the latter does not have pseudo-umbelliform inflorescences (they are pseudo-racemose) and it occurs only in Central America. Mucunaargentea has a pseudo-umbelliform inflorescence; a peduncle 7 – 10 cm long; flowers 8 – 9 cm long; a yellow corolla; fruits with a dense indumentum, but no lamellate ornamentation; rounded seeds, with the hilum extending around nearly the whole circumference of the seed. This species is distinct because of the combination of primary bracts 3 cm long, which fall before anthesis, and the dense, appressed silvery hairs on the abaxial surface of the leaflets. M. argentea is morphologically most similar to M. elliptica, but the latter has erect, golden hairs on the abaxial surface of the leaflets and persistent bracts.

Extinction risk predictions for the world's flowering plants to support their conservation (2024). Bachman, S.P., Brown, M.J.M., Leão, T.C.C., Lughadha, E.N., Walker, B.E. https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.19592

Conservation

Predicted extinction risk: not threatened. Confidence: confident